Crystal growth and twinned crystal structure of Sr₂CaWO₆

Abstract

Single crystals of Sr(2)CaWO(6) have been prepared by sintering at high temperature. Powder samples were compressed into rods and heated up to 1953 K. This seems a promising new route for further studies of the structure and physical properties of double perovskites. The structural model of Sr(2)CaWO(6) includes a quantitative description of the twinning shown by the diffraction pattern that should be present in almost any single-crystal specimen for this type of compound.

Drastic Differences between the Local and the Average Structures of Sr2MSbO5.5 (M = Ca, Sr, Ba) Oxygen-Deficient Double Perovskites

“…It is informative to compare the Sr 2 MSbO 5.5 compounds with their oxygen stoichiometric tungsten analogs, Sr 2 MWO 6 , since W 6+ and Sb 5+ have similar ionic radii. The double-perovskite Sr 2 CaWO 6 crystallizes in space group P 2 1 / n as a result of octahedral tilting about all three perovskite unit cell axes. , Tilting of the B O 6 and B ′O 6 octahedra by not more than about 15° is very common in perovskites with tolerance factors below 1 and serves to reduce the coordination numbers of the A -site cations below 12 and shorten some of the remaining bonds. Since Sr 2 CaSbO 5.5 and Sr 2 CaWO 6 have essentially the same τ, it is worthwhile to consider why Sr 2 CaSbO 5.5 does not display a common pattern of octahedral tilting.…”

Crystal Growth and Structure Analysis of Ce18W10O57: A Complex Oxide Containing Tungsten in an Unusual Trigonal Prismatic Coordination Environment

“…Ternary oxides such as CaWO 4 , which adopt the common Scheelite structure, exhibit the tetrahedral coordination environment, whereas Ln 6 WO 12 (Ln = Y, Ho, Er, Yb), La 2 W 2 O 9 (Ln = La, Pr, Nd, Sm, Gd), M 2 (UO 2 )­(W 2 O 8 ) (M = Na, K), Ba 3 WO 6 , Ba 2 WO 5 , Ba 3 W 2 O 9 , Ba 3 MWO 6 (M= Mg, Zn), and Ba 3 Fe 2 WO 9 all contain tungsten in an octahedral coordination environment. The latter coordination environment is rather common in tungstates and is found as isolated, ,, corner-shared, ,− and edge-shared , motifs; very few examples, such as Ba 3 W 2 O 9 , A 6 Th 6 (WO 4 ) 14 O (A = K and Rb), and La 18 W 10 O 57 , contain tungsten in a face-shared coordination environment due to the electrostatic repulsion between the highly charged metal centers. , An exception to this generalization is found for cases where tungsten is present as W­(III), W­(IV), or W­(V), , which sufficiently reduces the tungsten–tungsten repulsion and where potential metal–metal bonding interactions can stabilize the arrangement. In a small number of reported structures, tungsten is found in other less common coordination environments that include distorted cubic coordination in Y 2 WO 6 , trigonal bipyramidal coordination in Ca 3 WO 5 Cl 2 , seven-coordinated WO 7 polyhedra in Re 10 W 22 O 81 (Ce, Nd), , and a trigonal prismatic arrangement in the oxychloride Ln 3 WO 6 Cl 3 (Ln = La, Pr). , …”

Investigation of crystal structure of SrLa(FeTi)O 6 and BaLa(FeTi)O 6 perovskites by rietveld refinement

“…The ordering often results in the double perovskite structure with the doubling of the primitive perovskite unit cell. To mention, examples of such double perovskite materials are NaLaMgWO 6 [King et al, 2009], SrLaCoRuO 6 [Kim et al, 1995& Bos et al, 2005, SrLaZnRuO 6 , SrLaMgRuO 6 , SrLaNdRuO 6 [Iturbe-Zabalo, Faik et al, 2013], SrPrMgRuO 6 ], SrLaZnRuO6, SrLaMgRuO6 [ Iturbe-Zabalo, Gateshki et al, 2013, SrLaCuNbO 6 , SrLaCuTaO 6 [West & Davies 2012], family of SrLnFeRuO 6 , where Ln are rare earth ions [ Iturbe-Zabalo, et al, 2012], Sr 2 FeReO 6 [Kobayashi et al, 1999], Sr 2 FeMoO 6 [Kobayashi et al, 2006], Sr 2 YTaO 6 and Sr 2 YNbO 6 [Howard et al, 2005], Sm 2 NaIrO 6 [Samuel et al, 2005], Sr 2 CaWO 6 [Madariaga et al, 2010]. These materials have been extensively studied due to their interesting structural, magnetic, electrical, electronic properties and applications.…”